Spinal dysraphism , classification , imaging and diagnosis

1. Dr.Pooja
Junior Resident
Department of Radiodiagnosis
Azeezia Medical College
Imaging in spinal dysraphism

2. Congenital malformations of the spine and spinal cord are
generally referred to as spinal dysraphisms
*Neural tube defects
* Spina bifida
In the spine, the most common congenital lesions
 diverse forms of spinal dysraphism
diverse forms of caudal spinal anomalies

3. IMAGING MODALITIES
 MRI :IOC
 PLAIN RADIOGRAPH:
 bony defects ,
 widened spinal canal ,
 scoliosis,
 segmentation anomalies like blockvertebra, butterfly
vertebrae ,bony spur (diastematomyelia)
 USG: antenatal Dx –open widened neural arch ,
meningomyelocele sac , hydrocephalus .
 CT :bonyspur

4. Spinal CordDevelopment
Summarized in three basic embryologic stages
The first stage : Gastrulation (the 2or 3week)
a bilaminar embryonic disk to a trilaminar disk.
The secondstage:primaryneurulation(weeks3–4)
the notochord and overlying ectoderm interact neural plate.
bends and folds  neural tube,
which then closes bidirectional in a zipperlike manner
The final stage :secondary neurulation (weeks 5–6),
 a secondary neural tube is formed by the caudal cell mass.
cavitation,  the tip of the conus medullaris and filum terminale
retrogressive differentiation.

5. 1.GASTRULATION

6. 2.Primary neurulation.
Formation of the Neural Plate
Shaping of the Neural Plate
Bending of the Neural Plate
Fusion

7. Anterior
neuropore
close by Day 25
Posterior
neuropore close
by Day 27
Anencephaly
Spina Bifida

8. Disjunction.
Upon completion of disjunction,
the cutaneous ectoderm fuses in
the midline, dorsal to the closed
neural tube.
Failure leads to Myelomeningocele.

9. Canalization and retrogressive
differentiation (synonym:
secondary neurulation).
Diagrammatic representation of
proposed embryogenesis.
3.SECONDARY NERULATION

12. OPEN SPINAL DYSRAPHISM (OSD)
 There is a defect in the overlying skin, and the neural tissue is
exposed to the environment.
 MYELOCELEAND MYELOMENINGOCELE
 Embryological defect : Complete nondisjunction of cutaneous ectoderm from
neural ectoderm.
 Neural folds do not fuse in the midline to form neural tube.
 Remain in continuity with the cutaneous ectoderm.
 This exposed part of the spinal cord is NEURAL PLACODE.
 MC location : Lumbosacral region >thoraco- lumbar region
 Imaging usually not done(clinically obvious)

13.  The main differentiating feature between a myelomeningocele and
myelocele is the position of the neural placode relative to the skin surface
 The neural placode protrudes above the skin surface with a myelomeningocele
and is flush with the skin surface with a myelocele
MYELOMENINGOCELE MYELOCELE

14. Myelomeningocele. Axial
schematic of myelomeningocele
shows neural placode (star)
protruding above skin surface
due to expansion of underlying
subarachnoid space (arrow).
Myelomeningocele.
Axial T2- weighted
MR image
Myelomeningocele.
Sagittal T2- weighted MR
image).

15. Myelocele.Axial schematic of
myeloceleshows neural placode
(arrow) flush with skin surface.
Myelocele. Axial T2-weighted MR
image in 1-day-old girl shows
exposed neural placode (arrow) that
is flush with skin surface, consistent
with myelocele. There is no
expansion of underlying
subarachnoid space

16. HEMIMYELOMENINGOCELE AND HEMIMYELOCELE
 Hemimyelomeningoceles and hemimyeloceles can also occur
but are extremely rare .
 These conditions occur when a myelomeningocele or myelocele
is associated with diastematomyelia (cord splitting) and one
hemicord fails to neurulate.

17. • Placode ulceration and infection are leading causes of mortality in
the untreated newborn, affected patients are operated on soon after
birth.
• MRI investigation should be performed whenever possible to
obtain:
(a)anatomic characterization of the various components of the
malformation, especially regarding the relationships
between the placode and nerve roots.
(b)presurgical evaluation of the entity and morphology of the
malformation sequence (hydromyelia, Chiari-II
malformation,and associated hydrocephalus)
(c)identification of rare caseswith associated cord splitting
(hemimyelomeningoceles andhemimyeloceles)

18. • All patients with OSDsalso harbor a Chiari-II
malformation,which is an element, rather than an associated
feature, of the diseasecommonly called
“myelomeningocele,” aswell asof the other forms of OSDs

19. CLOSED SPINAL DYSRAPHISM

20. CLOSEDSPINALDYSRAPHISMS
WITHASUBCUTANEOUSMASS
1. Lipoma with dorsaldefects
2. Myelocystocele(Terminal or cervical)
3. Meningocele
4. Cervical myelomeningocele

21. 1.Lipomas with a duraldefect
• lipomyeloceles and lipomyelomeningoceles.
• defect in primary neurulation whereby mesenchymal tissue
enters the neural tube and forms lipomatous tissue
• Characterized clinically by the presence of a
subcutaneous fatty mass above the intergluteal crease.
• Diff both based on lipoma – placode interface
• Lipomyelocele : interface within spinal canal
• Lipomyelomenigocele: Outside the spinal canal due to sub-
arachnoid space expansion.

22. Fig. 4—Lipomyelocele. A, Axial schematic of lipomyelocele shows
placode–lipoma interface (arrow) lies within spinal canal. B, Axial T2-
weighted MR image in 3-year-old girl shows placode–lipoma interface
(arrow) within spinal canal, characteristic for lipomyelocele. C, Sagittal
T1-weighted MR image in 3-year-old girl with lipomyelocele shows
subcutaneous fatty mass (black arrow) and placode–lipoma interface
(white arrow) within spinal canal.

23. Fig. 5—Lipomyelomeningocele. A, Axial schematic of
lipomyelomeningocele shows placode–lipoma interface (arrow) lies
outside of spinal canal due to expansion of subarachnoid space. B, Axial
T1-weighted MR image in 18-month-old boy shows
lipomyelomeningocele (arrow) that is differentiated from lipomyelocele
by location of placode–lipoma interface outside of spinal canal due to
expansion of subarachnoid space.

25. thehairytuftoverlying subcutaneouslipomas

26. 2. MENINGOCELE :herniation of CSF filled sac lined by dura and arachnoid matter .
Spinal cord not located within a meningocele but may be tethered to the neck of the sac
Posterior meningocele : posterior spina bifida  Lumbar/sacral
Anterior : Pre-sacral mostly

27. Fig. 6—Posterior meningocele. A, Sagittal T1-weighted MR image in in 12-month-old
girl shows posterior herniation of CSF-filled sac (arrow) in occipital region, consistent
with posterior meningocele. B, Sagittal T2-weighted MR image in 5-year-old boy
shows large posterior meningocele (arrow) in cervical region. C, Sagittal T2-weighted
MR image in 30-month-old girl shows small posterior meningocele (arrow) in lumbar
region.

28. ANTERIOR MENINGOCELE

29. 3.Myelocystocele
• Myelocystoceles are rare malformations
composed of a herniation of the spinal cord,
containing ahydromyelic cavity, within a
meningocele.
• Myelocystoceles are classified into terminal
and nonterminal, depending on whether the
malformation involves the apex of the conus
medullaris or an intermediate segment ofthe
spinal cord.

30. TERMINAL
MYELOCYSTOCELE
MYELOCYSTOCELE
(NON TERMINAL)
 Herniation of large
terminal syrinx
(syringocele) into a
posterior meningocele
through a posterior spinal
defect is referred to as a
terminal .
 The terminal syrinx and
meningocele components
do not usually
communicate with each
other
 Dilated central canal
herniates through a
posterior spina bifida
defect.
 covered with skin
 MC -cervical or
cervicothoracic regions

31. Fig. 8—Terminal myelocystocele. A, Sagittal schematic of terminal
myelocystocele shows terminal syrinx (star) herniating into large posterior
meningocele (arrows). B and C, Sagittal (B) and axial (C) T2-weighted MR
images in 1-month-old girl show terminal syrinx (white arrows) protruding
through large posterior spina bifida defect and herniating into posterior
meningocele component (black arrows). Sagittal image shows turbulent flow in
more anterior meningocele component (star, B).

32. NON TERMINAL MYELOCYSTOCELE
—Schematic of nonterminal myelocystocele
shows herniation of dilated central canal
through posterior spinal defect.

33. ClosedSpinalDysraphisms Without a
SubcutaneousMass
COMPLEX DYSRAPHIC STATES
A)Disorders of midline notochordal
integration
Dorsal neurentericfistula,
Neurenteric cyst
Diastematomyelia,
B)Disorders of notochordal formation,
Caudal agenesis
Segmental spinal dysgenesis.
SIMPLEDYSRAPHIC STATES
 Intradural lipoma,
 Filar lipoma,
 Tight filum terminale
 Persistent terminalventricle
 Dermal sinus.

34. 1. LIPOMA
2Types :Intradural lipoma and Filar lipoma
Embryological defect :focal premature disjunction of epidermalfrom
neural ectoderm.
1.INTRADURALLIPOMA
Lipoma within the duralsac
MC :Lumbosacralspine
a/w tethered-cord syndrome
2.FILAR LIPOMA
Fibrolipomatous thickening of the filum terminale is referred to asa
filar lipoma.
MR :T1hyperintense signal +thickened filum terminale

35. Intradural lipoma
Filarlipoma
, Sagittal (A) and axial (B) T1-weighted MR
images I with filar lipoma (arrows),
which has characteristic T1 hyperintensity and
marked thickening of filum terminale
.Sagittal T1-weighted (A) and sagittal T2- weighted fat-saturated (B) MR images show
large intradural lipoma (arrows), which is
hyperintense on T1-weighted image and hypointense on
T2-weighted fat-saturated image. Lipoma is attached to
conus medullaris, which is low lying.

36. 3. TIGHT FILUM TERMINALE
 hypertrophy and shortening of the filum terminale
 EMBRYOLOGY:incomplete involution of
the distal spinalcord during embryogenesis.
 This condition causes tethering of the spinal cord
and impaired ascent of the conus medullaris.
 The conus medullaris is low lying relative to its
normal position, which is usually above the L2–
L3disc level
Sagittal T2-weighted MR image in 12-month-old boy shows tight filum terminale, characterized
by thickening and shortening of filum terminale (black arrow) with low-lying conus medullaris.
Incidental cross-fused renal ectopia (white arrow) is also present.

37. Persistence of a small,
ependymal lined cavity within
the conus medullaris.
It is the widest part of the
central canal at the levelof
conus
point of union between the
portion of the central canal
made by neurulation and the
portion made by canalization
of the caudal cell mass
Imaging :Location –above the
filum terminale and lack of
contrast enhancment Persistent terminal ventricle.
A and B, Sagittal T2-weighted (A) and sagittal
T1-weighted contrast-enhanced (B) MR
images show persistent terminal ventricle as
cystic structure (arrows) at inferior aspect of
conus medullaris, which does not enhance
4.PERSISTENTTERMINAL VENTRICLE

38. Epithelial lined fistula that
connects neural tissue or
meninges to the skinsurface.
If the superficial ectoderm
fails to separate from the
neural ectoderm at onepoint.
MC :Lumbo sacralregion
C/F :midline dimple , hairy
naevus , hyperpigmented
patch /capillary hemangioma
Infectious complication if not
surgically treated
5.DERMAL SINUS

39. Fig. 14—Dermal sinus. A and B, Sagittal schematic (A) and sagittal T2-weighted
MR image (B) in 9-year-old girl show intradural dermoid (stars) with tract
extending from central canal to skin surface (black arrows). Note tenting of dural
sac at origin of dermal sinus (white arrows). C, Axial T2-weighted MR image from
same patient as in B shows posterior location of hyperintense dermoid (arrow).

40. COMPLEX DYSRAPHIC STATES
DISORDERS OF MIDLINE
NOTOCHORDAL
INTEGRATION
1. Dorsal enteric fistula,
2. Neurenteric cyst
3. Diastematomyelia,
DISORDERS OF NOTOCHORDAL
FORMATION
1. Caudal agenesis
2. Segmental spinal dysgenesis.
{Gastrulation is characterized by the development of the notochord, apotent
inductor that is involved in the formation of not only the spine and spinal cord, but
also of several other organs and structures in the human body; therefore, spinal
dysraphisms originating during this period will characteristically show a complex
picture in which not only the spinal cord, but also other organs are impaired.
Hence disorders of gastrulation are also called complex dysraphic states}

41. DISORDERS OF MIDLINE
NOTOCHORDAL INTEGRATION
1. DORSAL ENTERIC FISTULA
Abnormal connection between the skin surface and bowel.
2.NEURENTERIC CYSTS
 Localized form of dorsal enteric fistula
 ~ Mucin-secreting epithelium (~GItract )lined cyst
 MC :cervico-thoracic spine anterior to spinal cord

42. Fig. 15—Neurenteric cyst in 3-year-old girl. A and B, Sagittal T2-weighted (A) and
axial T1-weighted (B) MR images show bilobed neurenteric cyst (arrows)
extending from central canal into posterior mediastinum. C, Three-dimensional
CT reconstruction image shows osseous opening (arrow) through which
neurenteric cyst passes. This opening is called the Kovalevsky canal.

43. 3.DIASTEMATOMYELIA
 Separation of the spinal cord into two hemicords
 The two hemicords are usually symmetric, although thelength of
separation is variable.
 Type 1: Dual Dural-Arachnoid Tubes (Pang Type I) :
 the two hemicords are located within individual dural sacs
separated by an osseous or cartilaginousseptum
 In Type 2 : Single Dural-Arachnoid Tube (Pang Type II) :
 Single dural tube containing two hemicords, sometimes with an
intervening fibrous septum
 C/F:Hairy tuft , scoliosis , tethered cordsyndrome.

44. Fig. 16—Type 1 diastematomyelia. A–C, Sagittal T2-weighted MR (A), axial T2-
weighted MR (B), and axial CT with bone algorithm (C) images in 6-year-old boy
show two dural tubes separated by osseous bridge (arrows), which is characteristic
for type 1 diastematomyelia.

45. Fig. 17—Type 2 diastematomyelia. A–C, Sagittal T1-weighted (A), coronal T1-
weighted (B), and axial T2-weighted (C) MR images in 9-year-old girl show
splitting of distal cord into two hemicords (white arrows, B and C) within single
dural tube, which is characteristic for type 2 diastematomyelia. Incidental filum
lipoma (black arrows, A and B) is present as well.

46. II.DISORDERS OFNOTOCHORDAL FORMATION
1. CAUDALAGENESIS
Total or partial agenesis of the spinalcolumn
A/w anal imperforation, genital anomalies, renal dysplasia or aplasia,
pulmonary hypoplasia, or limb abnormalities.
2Types
Type 1: high positionof conus +abrupt termination of conus
medullaris(D11/12)+ sig neuro deficit
Type II:low position(L1) +tethering of conus medullaris

47. CAUDALAGENESIS
,
Fig. 18A —Caudal agenesis.
Sagittal T2-weighted (A) and
sagittal T1-weighted (B) MR
images in 6-month-old girl show
agenesis of sacrum.
Conus medullaris is high in
position and wedge shaped (arrow)
due to abrupt termination.
These findings are characteristic of
type 1 caudal agenesis.
Distal cord syrinx (arrowhead) is
present as well.

48. CAUDALREGRESSION SYNDROME
• Partial agenesis of the thoracolumbosacral spine
• Imperforate anus
• Malformed genitalia
• Bilateral renal dysplasia or aplasia
• Pulmonary hypoplasia
• Extreme external rotation and fusion of the lower
extremities (sirenomelia)
• Sacral agenesis arises early in gestation, probably
before the 10th week of gestation
• a/w diabetes mellitus,

49. CLASSIFICATION OF LUMBOSACRALAGENESIS
1. Type I :Total sacral agenesis +somelumbar vertebrae missing
2. Type II:Total SA +lumbar vertebrae not involved, severely shortening
transverse pelvic diameter
3. Type III: Subtotal SA +at least S-1 ispresent.
4. Type IV:Hemisacrum
1. IVA Total hemisacrum; all sacral segments present on one side, but entire
opposite side ismissing
2. IVB Subtotal hemisacrum, unilateral; all sacral segments present on one side,
only part of opposite sideis missing
3. IVC Subtotal hemisacrum, bilateral; part of each side is missing but to different
extents
5. Type V: Coccygeal agenesis
6. VATotal
7. VB Subtotal

50. 2.SEGMENTALSPINAL DYSGENESIS
Segmental agenesis or dysgenesis of
the thoracic or lumbar spine
+ segmental abnormality of the spinal
cord / nerve roots
+ congenital paraparesis / paraplegia,
+ congenital lower limb deformities.
Three-dimensional CT reconstruction image
(A) in 4-year-old girl and schematic illustration
(B) show multiple segmentation anomalies in
lumbar spine (superior to inferior
beginning at level of arrow):
partial sagittal partition,
butterfly vertebra,
hemivertebra,
tripedicular vertebra
widely separated butterfly
vertebra